27-09-2014, 10:20 AM
Machine Guns
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Introduction
To understand how machine guns work, it helps to know something about firearms in general. Almost any gun is based on one simple concept: You apply explosive pressure behind a projectile to launch it down a barrel. The earliest, and simplest, application of this idea is the cannon.
A cannon is just a metal tube with a closed end and an open end. The closed end has a small fuse hole. To load the cannon, gunpowder (a mixture of charcoal, sulphur and potassium nitrate) is poured in, and then a cannonball is dropped in. The gunpowder and cannonball sit in the breech, the rear part of bore, which is the open space in the cannon. To prepare the gun for a shot, a fuse (a length of flammable material) is run through the hole, so it reaches down to the gunpowder. To fire the cannon, light the fuse. The flame travels along the fuse, and finally reaches the gunpowder.
When gunpowder is ignited, it burns rapidly, producing a lot of hot gas in the process. The hot gas applies much greater pressure on the powder side of the cannonball than the air in the atmosphere applies on the other side. This propels the cannonball out of the gun at high speed.
The first handheld guns were essentially miniature cannons; first load some gunpowder, a steel ball and lit a fuse. Eventually, this technology gave way to trigger-activated weapons, such as the flint-lock gun and the percussion cap.
Flintlock guns ignited gunpowder by producing a tiny spark, while percussion caps used mercuric fulminate, an explosive compound you could ignite with a sharp blow. To load a percussion cap gun, you poured gunpowder into the breech, stuffed the projectile in on top of it, and placed a mercuric fulminate cap on top of a small nipple. To fire the gun, you cocked a hammer all the way back, and pulled the gun's trigger. The trigger released the hammer, which swung forward onto the explosive cap. The cap ignited, shooting a small flame down a tube to the gunpowder. The gunpowder exploded, launching the projectile out of the barrel.
FULLY AUTOMATIC
The Gatling gun is often considered a machine gun because it shoots a large number of bullets in a short amount of time. But unlike modern machine guns, it is not fully automatic. You have to keep cranking if you want to keep shooting. The first fully automatic machine gun is credited to an American named Hiram Maxim. Maxim's remarkable gun could shoot more than 500 rounds per minute, giving it the firepower of about 100 rifles.
The basic idea behind Maxim's gun, as well as the hundreds of machine gun designs that followed, was to use the power of the cartridge explosion to reload and re-cock the gun after each shot. There are three basic mechanisms for harnessing this power:
• Recoil systems
• Blowback systems
• Gas mechanisms
The first automatic machine guns had a recoil-based system. In nature, every action has an equal and opposite reaction. This principle is responsible for the recoil effect in guns. When you propel a bullet down the barrel, the forward force of the bullet has an opposite force that pushes the gun backward.
In a gun built like a revolver, this recoil force just pushes the gun back at the shooter. But in a recoil-based machine gun, moving mechanisms inside the gun absorb some of this recoil force.
CONCLUSION
Gun manufacturers are continually adding new modifications to machine guns, but the basic mechanism has remained the same for more than a hundred years. Whether or not we have ever held a machine gun, or even seen one, this device has had a profound effect on our life. Machine guns have had a hand in dissolving nations, repressing revolutions, overthrowing governments and ending wars.